Circuit breaker with improved armature adjustment means and armature pivot means



July 12, 1966 w. 1. s'rEPHENsoN, JR., ETAL 3,260,322

CIRCUIT BREAKER WITH IMPROVED ARMATURE ADJUSTMENT MEANS AND ARMATURE PIVOT MEANS Original Filed March 2, 1960 6 Sheeizs-Sheetl l 1 July 12, 1966 w. sTEPHENsoN, JR; ETAL 3,260,822

CIRCUIT BREAKER WITH IMPROVED ARMATURE ADJUSTMENT MEANS AND ARMATURE PIVOT MEANS Original Filed March 2, 1960 6 Sheets-Sheet 2 Fig.2.

July 12, 1966 w. 1. s'rEPHENsoN, JR., ETAL 3,260,322

CIRCUIT BREAKER WITH IMPROVED ARMATURE ADJUSTMENT MEANS AND ARMATURE PIVOT MEANS Original Filed March 2, 1960 6 Sheets-Sheet ."5

July 12, 1966 w` l. s'rEPHENsoN, JR., ETAL 3,260,822

CIRCUIT BREAKER WITH IMPROVED ARMATURE ADJUSTMENT MEANS AND ARMATURE PIVOT MEANS Original Filed March 2, 1960 6 Sheets-Sheet 4 Figs.

Fig .7,

July 12, 1966 w. l. sTEPHENsoN, JR.. ETAL 3,260,822

CIRCUIT BREAKER WITH IMPROVED ARMATURE ADJUSTMENT MEANS AND ARMATURE PIVOT MEANS July 12 1966 w` l. sTEPHENsoN, JR., ET AL 3,260,822

CIRCUIT BREKER WITH IMPROVED A RMATURE ADJUSTMENT MEANS AND ARMATURE PIVOT MEANS Original Filed March 2, 1960 6 Sheets-Sheet 6 Fig. I6

United States Patent O CIRCUIT BREAKER WITH IMPROVE!) ARMATURE 1AIIIJNSIMENT MEANS AND ARMATURE PIVOT William I. Stephenson, Jr., Beaver, and Eugene J. Walker,

Borough Township, Beaver, Pa., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Original application Mar. 2, 1960, Ser. No. 12,379, now Patent No. 3,211,860, dated Oct. 12, 1965. Divided and this application Feb. 3, 1965, Ser. No. 430,116

8 Claims. (Cl. 200-88) This application is a division of the parent application Serial No. 12,379, led March 2, 1960, now Patent No. 3,211,860, issued October 12, 1965.

This invention relates, generally, to circuit breakers and, more particularly, to enclosed circuit breakers wit-h automatic tripping means.

One object of the invention is to provide an improved circuit breaker of compact construction which is simple and inexpensive to manufacture and sa-fe and reliable in operation.

Another object of the invention is to provide a circuit breaker having a rotatable trip bar with improved means for rotatably supporting the tr-ip bar within the circuit breaker.

Another object of the invention is to provide a circuit breaker having an adjustable trip device with improved means for achieving an initial adjustment or calibration during the assembly of the trip device.

A still further object of the invention is to provide a circuit breaker having an electro-magnetic trip device with improved means for supporting the armature on the magnetic yoke of the trip device.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both las to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description o-f one embodiment thereof when read in conjunction with the accompanying drawings, in which:

FIGURE 1 is a side view in section of a circuit breaker constructed in accordance with the invention, the breaker being shown in the open position;

FIG. 2 is a plan View, on an enlarged scale, of the removable trip device of the breaker shown in FIG. 1;

FIG. 3 is a front view, with almost all of the cover broken away, of the trip device;

FIG. 4 is an enlarged sectional view taken along lines IV-IV of FIG. 3;

FIG. 5 is an elevational View on an enlarged scale of the insulating and supporting base of the trip device;

FIG. 6 -is a sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is a sectional view taken along line VIL-VII of FIG. 5;

FIG. 8 is an elevational view on an enlarged scale of the insulating cover of the trip device;

FIG. 9 is a plan view of the trip device cover shown in FIG. 8;

IFIG. 10 is a sectional view taken along lines X--X of FIG. 8;

FIG. 1l is an elevational view of a barrier that cooperates with the partition portions of the insulating trip device base and cover to enable isolation of the pole units of the trip device;

FIG. 12 is an elevational detailed view, on an enlarged scale, of the trip bar shown in FIG. 3;

FIG. 13 is a plan View ofthe trip bar shown in FIG. 12;

FIG. 14 is an elevational view on an enlarged scale of 3,260,822 Patented July 12, 1966 1orie o; the magnetic yokes of the trip device shown in FIG. 15 is an end view of the magnetic yoke shown in FIG. 14 looking in the direction of the arrows;

FIG. 16 is an elevational View on an enlarged scale of oni:i of the armatures for the trip device shown in FIG. 3; an

FIG. 17 is an end View of the armature shown in FIG. 16 looking in the direction of the arrows.

Referring to FIG. 1 of the drawings, the circuit breaker shown therein comprises, generally, a base 11 and a removable cover 13 both of which may be molded from a suitable insulating composition. The breaker is of the three-pole type, each pole bein-g provided with terminals at pposite ends of the base 11 indicated generally at 15 an 17.

The circuit breaker includes a stationary contact 21, a movable contact 23 and an arc extinguisher indicated generally -at 25, for each pole unit. A common operating mechanism indicated generally at 27 is provided for simultaneously actuating the three movable contacts to open and closed positions. A trip device indicated generally at 29 serves to eifect automatic opening of the breaker contacts in response to predetermined over-load conditions in a circuit through any pole unit of the breaker.

The terminal 15 is disposed at the outer end of a conducting strip 311 which extends into t-he housing and rigidly supports the stationary contact 21. The movable contact 23 for each pole unity is mounted on a rigid contact arm 33 which is supported on a switch arm 35 secured to a tie bar 37 which extends across all of the pole units 4of the breaker and supports the switch arms for the several pole units for unitary movement to open and closed positions. The ,contact arm 33 is connected by means of a flexible conductor 39 to an intermediate or trip unit terminal member or conductor 41 which is secured at one end thereof to the base 11 by a screw 42. The conducting member 41 extends through the trip unit 29 and is connected 4at its outer end to the terminal structure 17 The operating mechanism 27 is disposed in the center compartment of the housing and is supported by a pair of spaced `frame members 53 (only one being shown) which are secured to the base 11. The operating mechanism comprises a p-ivoted forked operating lever 55, a toggle comprising toggle links 57 and 59, over-center spring means 61 and a pivoted releasable cradle 63 which is controlled by the trip device 29. An arcuate insulating shield 67 for substantially closing an opening 619 in the cover 13 is mounted on the end of the operating lever 55 and has an integral handle portion 71 extending out through the opening 69 to permit manual operation of the breaker.

The toggle links 57 and 59 are pivotally connected together by a knee pivot pin 73. One end of the toggle link 57 is bifurcated to straddle a pin 75 which is integral with the cradle 63. The toggle link S9 is pivotally connected to the switch arm 35 for the center pole unit, by a pin 77. The over-center springs 61 are connected under tension between the outer end of the operating lever 55 and a plate member 78 which is attached to the knee pin 73 of the toggle 57, 59. The circuit breaker is manually operated to the open position by movement of the handle 71 in a counterclockwise direction to the oil position, which movement actuates the over-center springs 61 to cause collapse of the toggle 57, 59 and opening movement of the switch arms 35 for all of the pole units of the breaker in a well-known manner. The breaker is shown in the open position in FIG. 1.

The circuit breaker is manually closed by reverse movement of the handle 71 from the off to the on position, which movement causes the over-center springs 61 to straighten the toggle 57, 59, thereby moving the switch arms 35, for all of the pole units, to the closed position in a manner well-known in the art.

Referring to FIGS. 2, 3 and 4, the trip device 29 comprises an insulating base or support member 81 secured by means of rivets 33 (only one being shown in FIG. 4), or other suitable means, to a bracket 85 which is, in turn, secured to the base 11 of the circuit breaker by means of the screw 42 (FIG. 1). A cover 89 of insulating material cooperates with the insulating base 81 to enclose the trip device 29. The electro-responsive tripping means for the three pole units are the same, therefore, only the means for the center pole will be specifically described. The conducting member 41 for each pole unit has a looped portion 91 one leg of which is disposed adjacent to the base 81 and secured to the base by means of the rivets 83. A bimetallic element 93 has one end secured by means of rivets 95 to the other leg of the loop 91 of the conducting member 41. The rivets 95 also serve to secure the loop 91 and bimetal 93 to a bracket 97 that is secured to the trip unit base 81 by means (not shown) and that also supports the electro-magnetic trip means which will be hereinafter described. The free end of the bimetal 93 is disposed adjacent an adjusting screw 101 which is threaded into a tapped opening in a supporting member 103 that is attached by means of a rivet 105 to a trip bar 107. The trip bar 107 is rotatably supported in the trip device by means of the bracket 85 in a manner which will be hereinafter described. Spring means 109 and 111 are provided on opposite sides of the pivot of the trip bar 107 to keep the trip bar from rotating when the circuit breaker is jarred or jolted, thereby acting as an anti-shock device. The bias of the spring 111 against the base 81 is adjusted by means of screw 113 in order to adjust the trip bar 107 to give the proper latch engagement which will be later described. In the normal position of the trip bar 1117, a latch member 115 rigidly imbedded therein, engages a latch portion 117 of a latching mechanism which is indicated generally at 119 and which restrains the cradle 63 in the latched position shown in FIG. l. The high expansion side of the bimetal element 93 is to the left as viewed in FIG. 4. When this element is heated a predetermined amount in response to over-load currents, it deflects to the right to engage the adjusting screw 101 to rotate the trip bar 107 clockwise, as viewed in FIG. 4, about its pivot indicated generally at 121 causing the latch 115 to release the latch portion 117 of the latching mechanism 119, thus freeing the cradle 63 (FIG. 1). Although the breaker is shown in the open position in FIG. 1, it can be understood that the electro-responsive trip device 29 will operate only when the contacts are closed and a circuit is energized through the breaker. When the breaker is closed and the bimetal 93 operates to effect release of the latching mechanism 119 to release the cradle 63 (FIG. l), the springs 61 rotate the cradle 63 in a clockwise direction, as viewed in FIG. 1, about its pivot 122 to cause collapse of the toggle 57, 59 and movement of the switch arms 35 and movable contacts 23 for all of the pole units of the breaker to the open circuit position. This movement also effects movement of the handle portion 71 to an intermediate position to indicate that the circuit breaker has tripped open. The breaker cannot be closed after a tripping operati-on until the handle 71 is moved to the fully open position during which movement a projection 123 of the bracket 55 engages a shoulder 125 of the cradle 63 rotating the cradle in a counterclockwise direction about its pivot 122 until the cradle 1re-engages the latching mechanism 119. After the cradle 63 has been relatched, the operating handle 71 can then be moved to the on position to effect closing of the contacts for all of the pole units in the same manner previously described.

The trip device 29 is also provided with electro-magnetic tripping means, indicated generally at 127, for each of the pole units of the breaker. The electro-magnetic tripping means 127 operates in response to over-loads above a predetermined Value, or in response to short circuits, to instantaneously actuate the trip bar 107 to trip the circuit breaker. Each electro-magnet comprises a fixed U-shaped laminated magnetic core member or yoke indicated generally at 129 and best illustrated in FIGS. 14 and 15, the laminations being secured together by means of rivets 131 (FIGS. 3 and 14). Each core member 129 is supported on the bracket 97 (FIG. 4) by means of two rivets 132 (FIG. 3). An armature indicated generally at 133 (FIGS. 16 and 17), which comprises a number of laminations secured together by means of rivets 135 (FIG. 16), is pivotally supported on one leg 137 (FIGS. 3 and 14) of the magnetic yoke 129 in a V- shaped pivot which will be hereinafter described. Referring to FIGS. 3 and 4, each of the armatures 133 is biased to the open position by means of two springs 140 which are supported under tension between a projection 136 of the magnetic yoke 129 and a projection 138 of the armature 133. An operating rod 139 having a head portion 141 is pivotally attached at its lower end to the armature 133 by means of a pin 143. The operating rod 139 extends through an opening in a metallic bracket 144 that is rigidly secured to the trip bar 107. Upon the occurrence of an over-load current above a predetermined value or in response to short circuits, in any of the pole units, the current in the conducting member 41, which passes through the opening defined by the legs of the U- shaped magnetic yoke 129 (FIG. 3), energizes the magnetic yoke causing the yoke to attract the armature 133. The armature 133 thereupon pivots, about the leg 137 of the yoke 129, against the bias of the springs 140, pulling the operating rod 139 downward whereupon the head portion 141 of the operating rod engages the bracket 144 on the trip bar 107 rotating the trip bar in a clockwise direction as viewed in FIG. 4 to effect release of the cradle 63 (FIG. 1) and tripping of the breaker in the manner previously described.

The electromagnetic is adjusted by means of an adjusting rod or cam follower indicated generally at 147 (FIGS. 3 and 4) which extends at its upper end through an opening in a bracket 149, that is attached to the trip unit base 81. The cam follower 147 extends, at its lower end, through an opening 151 (shown in dotted lines in FIG. 14) in a bracket 153 of magnetic material which extends from one leg of the magnetic yoke 129 and which functions not only to support the cam follower 147 but to exert a back pull on the armature 133. The upper end of the cam follower 147 engages a cam surface 155 (shown in dotted lines in FIGS. 3 and 4) on an adjusting member 157.

The adjusting member 157 is biased outwardly by a spring 161 which is disposed between the upper surface of a supporting plate 162 `and a lower surface of a ange 163 which is molded integral with the adjusting member 157. There are a number of detents (not shown) in the cam surface which receive the upper end of the cam follower 147 in order to positively position the member 147 to permit accurate adjustment of the electro-magnetic trip device 127. The adjusting member 157 is provided with a slot 165 (FIGS. 2 and 4) into which a screwdriver or other tool can be inserted to permit manual adjustment of the electro-magnetic trip device 127. The magnetic air gap between the armature 133 and the magnetic yoke 129 in each pole unit, is varied by rotation of the adjusty ing member 157 which movement rotates the cam surface 155 to move the cam follower 147 vertically, as seen in FIGS. 3 and 4, to thereby move the armature 133 about its pivot against the bias of the springs 140. As seen in FIG. 2, there are markings on the trip unit cover 89 that indicate the positions of the rotatable adjusting members 157 to thereby indicate the minimum amount of over-load current through any pole unit that will effect a magnetic tripping operation.

Improved means are provided for permitting an accurate and fine calibration of the electro-magnetic trip device 127. Because the trip unit parts are manufactured and assembled in mass production, it can be understood that additional adjusting means is required in order to permit a tine calibration of each individual electro-magnetic trip device. As best illustrated in FIG. 3, the cam follower 147 is comprised of two parts 171 and 173. The upper portion of the lower part 173 is tapped to receive `the lower portion of the upper part 171 which is threaded so that the length or vertical dimension of the cam follower 147 can be varied by rotating one of the parts 171 or 173 with respect to the other. During the assembly of the trip unit 29, a worker can test the unit and vary the length of the cam follower 147 until the electromagnet 127 effects a tripping operation upon the occurrence of a selected predetermined over-load current indicated by the position of the adjusting member 157 in relation to the markings (FIG. 2) on the trip unit cover 89. The joint between the members 171 and 173 can be cemented fast when the cam follower 147 is the correct length. Thus, an accurate, fine calibration of each individual pole unit can be readily effected.

In electromagnets embodying a clapper-type armature, there is a tendency for the armature to walk out of the pivot, i.e., to move in a direction normal to the plane in which the armature rotates, until the armature falls out of position. On the circuit breakers presently in use, side plates or brackets are provided to keep the armature in place. Improved means are provided for keeping the armature in position on the magnetic yoke without the use of any additional parts other than the armature and the magnetic yoke. Referring to FIG. 15, it will be seen that the magnetic yoke 129 comprises a plurality of inner laminations 177 which are sandwiched between two thicker outer laminations 179. As seen in dotted lines in FIGS. 14 and 15, a V-shaped slot 181 is provided in the inner laminations 177; the two outermost laminations 179 forming side walls at opposite ends of the slot 181. Referring to FIG. 17, the armature 133 comprises a plurality of inner laminations 183 sandwiched between two thicker outer laminations 135. The inner laminations 183 form a V-shaped pivoting portion at one end of the armature 133, the outer laminations 185 being cut away as shown in FIGS. 16 and 17. As best illustrated in FIGS. 3 and 4, the V-shaped or knife-edge pivoting portion of the inner laminations 133, of the armature 133, is positioned in the V-shaped pivot of the inner laminations 177 of the magnetic yoke 129 when the parts are in place. The magnetic yoke outer laminations 179 keep the armature 133 from moving or walking out of position during operation of the electro-magnet 127.

The circuit breaker insulating base 11 and cover 13 (FIG. l) are provided with two sets of partition walls 191 and 193 (only one set being shown in FIG. l) which cooperate `to isolate the pole units of the portions of the circuit breaker adjacent the operating mechanism 27 and arc chutes so that gases formed upon the extinction of the arcs, during an opening operation, will not cause flashovers between the pole units. The heat and pressure generated upon arc extinction force gases back into the enclosed trip device 29 through openings to be hereinafter described, and these gases could cause flashover between the pole units of the trip device.

Means, therefore, are provided for preventing the passage of gases between the pole units of the enclosed trip device 29. As seen in FIG. 5, there is an opening 195, for each pole unit, provided in the trip unit base 81 to permit passage of the conducting member 41 (FIG. 4). An opening 197 (FIG. 5) is provided in the center pole unit portion of the base 8-1 to allow passage of the latch portion 117 (FIG. 4) which is part of the latching mechanism `119. Two openings 199 (FIG. 5) are also provided in the center pole unit portion -of the trip unit base 81 to allow passage of two arm members 201 (FIGS. 2 and 4) which members rotatably support the trip bar 107 in a manner to be hereinafter described. The openings 195, 197 and 199 are large enough to permit easy and quick assembly of the trip device 29 and to permit easy and quick mounting of the trip device in the circuit breaker. These openings, therefore, are not completely closed when the trip device is assembled, and gases, formed upon the extinction of the arcs during an opening operation, pass back into the trip device. Means therefore, are provided for preventing passage of these gases between the pole units of the trip device.

Referring to FIGS. 5, 6 and 7, there are two partition portions 203, molded integral with the insulating trip unit base 81, that divide the base into three compartments for the three pole units of the trip device. A semicircular opening 205 is provided in each of the partition portions 203. A rectangular opening 206 is also'provided in each of the partition porti-ons 203. A slot 207 is provided in the partition portions 203 adjacent each of the openings 206. The edges of the partition portions 203 comprise three surfaces 215, 216 and 217. As best seen in FIG. 6, the surfaces 215 and 217 are in different planes, and they are connected by the slanting surface 216.

Referring to FIGS. 8, 9 and l0 there are two partition portions 219, molded integral with `the insulating trip unit cover 89, that divide the cover into three compartments corresponding to the three compartments in the trip unit base 89. A semicircular opening 221 is provided in each of the partition portions 219. A generally rectangular opening 222 is provided in each of the partition portions 219 and a slot 223 is provided in lthe partition portions adjacent each of the openings 222. The edges of the partition portions 219 comprise three surfaces 225, 226 and 227. The surfaces 225 and 227 are in different planes, and they are connected by the slanting surface 226.

When the cover 89 is placed over the base 81, the partition portions 219 of the cover 89 cooperate with the partition portions 203 of the base 81 to form partition walls between the compartments of the trip device. The surfaces 225, 226 and 227 -of `the edges of the partition portions 219 mate with the surfaces 215, 216 and 217, respectively, of the edges of the partition portions 203 providing irregular mating connecting surfaces that are lapped together lto provide an effective seal between the compartments of the trip device.

The openings 205 in the base 81 cooperate with the openings 221 in the cover 89 to permit extension of the common trip bar 107 (FIG. 3) into each of the three pole units of the trip device 29. As seen in FIGS. 2, 3, 12 and 13, the trip bar 107y is provided with cylindrical flanges 225 which fit on opposite sides of the partitions that separate the trip unit compartments. The flanges 225 cooperate with the general mass of the trip bar 107 to close the openings 2,05, 2,21 in lthe trip unit partition walls.

The openings 206, 222 are provided to permit easy assembly of the springs 1,40 (FIG. 3) in the trip device. An insulating barrier 229 (FIG. l1) is provided for each of the partition walls 2,03, 219, (FIGS. 5-10) to fit into the slots 207 and 223 adjacent the openings 206, 222 to thereby close off` each of the openings 206, 222 in the trip unit partiti-on walls.

It can be understood that the irregular mating surfaces of the edges of the partition walls 203, 219, the flanges 225 on the trip member 107, and the barriers 229 all l cooperate to effectively isolate the three pole units of the .trip device 29 preventing passage of gases between the compartments and providing insulation between the live parts `of the different pole units.

As was previously mentioned, when the trip bar 107 is in place in the trip device, the fianges 225 are positioned on opposite sides of each of the partition walls 203, 219 to cooperate with the general mass of the trip bar to thereby close the `openings 205, 221 in the partition walls. It can be understood that during the assembly of the trip device 29, the amount of side movement of the trip bar 107 should be kept to a minimum in order that the flanges 225 on the trip bar 107 can be molded closely together so that they will be positioned close to the partition walls 203, 219 to more effectively close the openings 205, 221. It can be understood also that the trip bar 107 must be positively positioned in the trip device for proper latch engagement between the latch member 115 (FIG. 4) and the latch portion 117 of the latching mechanism 119.

Improved means, therefore, are provided for rotatably supporting the trip bar 107 within the trip device 29. Referring to FIG. 12, the trip bar 107 is provided with two metallic pins 231 that are rigidly embedded in the molded trip bar during the molding operation. An opening 233 is provided in the trip bar 107 near the outer end of each of the pins 231. As best illustrated in FIG. 2, these openings 233 provide access to the two independent supporting arms 201 (FIGS. 2 and 4) each of which has an opening near its inner end to receive one of the pins 231 whereby the trip bar 107 is rotatably supported on the supporting arms 201. Each of the supporting arms 201 extends through one of the openings 199 (FIG. 5) in the trip unit base 81 and is supported at its outer end on the bracket 85 (FIGS. 2 and 4) by means of a screw 237. Each of the supporting arms 201 is positively positioned with respect to the supporting bracket 85 by means of two dowels 241 and 243 (FIG. 4) in the bracket 85. Each of the arms 201 rests on top of one of the dowels 241 and receives the other dowel 243 in a semicircular opening in the end of the arm. During the assembly of the trip device 29, the `supporting arms 201 are placed over the pins 231 in the trip bar 107 and, with the trip unit cover 89 removed, the two arms 201 are placed through the openings 199 in the trip unit base 81 (FIG. 5). Each of the arms 201 is then positively positioned with -respect to the bracket 85 by means of two dowels 241 and 243 (FIG. 4). The arms are then fastened securely to the bracket 85 by means of 4the screws 237. It can be understood that there is no side movement required of the trip bar 107, with respect to the trip unit base 81, during the assembly of the trip device 29, and therefore, the flanges 225 on the trip bar 107 can be molded close enough together -to more effectively function as barriers aiding to isolate the compartments of the trip device.

Having described the invention in accordance with the patent statutes, it is to be understood that various changes and modifications may be made in the structural details and combinations of elements without departing from some of the essential features of the invention.

We claim` as our invention:

1. A circuit breaker having relatively movable contacts and means releasable to effect automatic opening of said contacts, electro-magnetic trip means including a core member and an armature, said armature upon the occur- Irence of an over-load current above a predetermined value moving towards said core member to close an air gap therebetween to effect release of said reileasa-ble means, adjusting means for adjusting said trip means by varying the dimension of said air gap, said adjusting means cornprising a cam member and a cam` follower, said cam fol- '.lower being disposed between said cam member and said armar-ure and being movable by movement of said cam member to move said armature to vary said magnetic air gap, and said cam follower being adjustable to vary said magnetic air gap to permit calibration of said electromagnetic trip means.

2. A circuit breaker having relatively movable contacts and means releasable to effect automatic opening of said contacts, electro-magnetic trip means including a core member and an armature, said armature upon the occurrence of an over-load current above a predetermined value moving towards said core member to close an air gap between said armature and core member to effect release of said lreleasable means, adjusting means for adjusting said trip means by varying the dimension of said air gap, said adjusting means comprising a cam member and a `cam follower, said cam follower being disposed between said cam member and said armature and being movable by movement of said cam member to thereby move said armature to vary said magnetic air gap, and means `for varying the length of said cam follower to thereby vary said magnetic air gap.

3. A circuit breaker having relatively movable contacts and means releasable to effect automatic opening of said contacts, electro-magnetic trip means including a core member and an armature, said armature upon the occurrence of an over-load current above a predetermined value moving towards said core member to close an air gap therebetween to effect release of said releasable means, adjusting means comprising a earn member having a cam surface and supported a distance away from said armature, an elongated member `disposed 'between said cam member and said armature, means biasing said armature against said elongated member, said elongated member upon movement of said cam member following said cam surface to effect movement of said armature relative to sai-d core member to vary said air gap to thereby vary the minimum amount -of over-load current that will effect a magnetic tripping operation, and said elongated member being adjustable to vary said air gap to permit calibration of said electro-magnetic trip means.

4. A circuit breaker having relatively movable contacts and means releasable to effect automatic opening of said contacts, electro-magnetic trip means including a core member and an armature, said armature upon the occurrence of an over-load current above a predetermined value moving towards said core member to close an air gap between said armature and core member to effect retlease of said releasable means, adjusting means including a manually rotatable cam member having a cam surface and supported a distance away from said armature, an adjustable member supported between said cam member and said armature, means lbiasing said armature against said adjustable member, said adjustable member upon rotation of said cam member following said cam surface to effect movement of said armature relative to said core member to vary said air gap to thereby vary the minimum amount of over-load current that will effect a magnetic tripping operation, said adjustable member including a first part having a tapped end and a second part having a threaded end screwed into said tapped end of said first part whereby rotation of one of said parts relative to the other will change the length of said adjustable member to enable calibration of said electro-magnetic trip means.

v5. A trip device for a circuit interrupter operable to effect opening of said interrupter, said trip device comprismg an energizing winding, a U-shaped core member -disposed to be energized by said winding, said core member comprising two outermost laminations and at least one inner lamination, a V-shaped pivot formed in one leg of said inner lamination, said outermost laminations forming side walls adjacent the opening defined by the legs. of said V-shaped pivot, a movable armature cornprising two outermost laminations and at =least one inner lamination, a knife-edge pivoting portion formed by said armature inner lamination and disposed in said core memmer V-shaped pivot to pivotally support said armature on said one leg of said core member, and said armature upon the occurrence of over-load currents above a predetermined amount pivotally moving towards the other leg of said U-shaped core member to effect automatic opening of said circuit interrupter.

6. A trip device for a circuit interrupter operable to effect -opening of said interrupter comprising an energizing winding, a -U-shaped core member disposed to be energized by said winding, said core member comprising two outermost laminations and a plurality of inner laminations, a V-shaped pivot formed in one leg of said inner laminations, said outermost Alaminations forming side walls adjacent the opening defined by the legs of said V-shaped pivot, a movable armature comprising two outermost laminations and a plurality of inner laminations, a knife-edge pivoting portion tormed by said armature inner laminations and disposed in said core member V-shaped pivot to pivotally support said armature on said one leg of said core member, and said armature upon the occurrence of over-load currents above a predetermined amount pivoting to effect automatic opening of said circuit interrupter.

7. A circuit breaker having relatively movable contacts and a trip device for effecting automatic opening of said contacts, said trip device comprising an energizing winding, a U-shaped core member disposed to be energized by said winding, said core member comprising two outermost laminations and at least one inner lamination, a V-shaped pivot formed lon one leg of said inner lamination, said outermost laminations forming sidewalls adjacent the opening defined by the legs of said V-shaped pivot, a movable armature comprising two outermost laminations and at least one inner lamination, said inner lamination comprising a knifeedge pivoting portion pivot ally supported on said V-shaped pivot on said one leg of said core member, said armature extending over the other leg of said core member and being spaced from said other leg rwhereby there is an air gap between said armature and said other leg, said armature upon the occurrence of an overload cur-rent above a predetermined value through said energizing winding pivoting toward said other yleg to close said air gap to effect automatic opening of said contacts, said side walls of said core member engaging said pivoting portion of said armature to prevent movement of said armature in a direction normal to a plane generated by said pivotal movement of said armature, means for adjusting said trip device by varying the dimension of said air gap, said adjusting means comprising a cam member and a cam follower, said cam follower being disposed between said cam member and said armature and being movable by movement of said cam member to move said armature to vary said magnetic air gap, and said cam follower being aljustable to vary said magnetic air gap to permit calibration of said trip device.

8. A circuit breaker comprising relatively movable contacts and a trip device for effecting automatic opening of said contacts, said trip device comprising an energizing winding, a U-shape-d core member disposed to be energized by said winding, said core member comprising two outermost laminations and at least one inner lamination, a V-shaped pivot formed in one leg of said inner lamination, said outermost laminations forming sidewalls adjacent the opening delined by the legs of said V-shaped pivot, a movable armature comprising a V-shaped pivoting portion disposed in said core member V-shaped pivot to pivotally support said armature on said one leg of said core member with said armature extending over the other leg of said core member spaced from said other leg whereby a magnetic air gap is formed between said armature and said other leg, said armature upon the occurrence of overload currents above a predetermined amount pivotally moving toward said other leg to close said air `gap to effect automatic opening of said circuit breaker, said sidewalls of said core mem-ber engaging said V- shaped pivoting portion of said armature to prevent movement of said armature on said core member in a direction normal to a plane generated by said pivotal movement of said armature, adjusting means comprising a cam member having a team sur-face, said cam member being supported a distance away from said armature, an elongated member Idisposed between said cam member and said armature, means biasing said armature against said elongated member to provide said air gap between said armature and said other leg, said elongated member upon movement of said cam mem-ber following said cam surface to effect movement of said armature relative to said other leg to vary said air gap to thereby vary the minimum amount off over-load current that will effect a magnetic tripping operation, said elongated member comprising a first part having a tapped end and a second part having a threaded end screwed into said tapped end of said first part whereby rotation of one of said parts relatiwe to the other will 4change the length of said elongated member to vary said `air gap to thereby calibrate said trip device.

References Cited by the Examiner UNITED STATES PATENTS 2,574,093 11/ 1951 Edmunds 200-88 2,644,120 6/1953 Swanton 317-'187 2,824,925 2/1958 Grissinger et al 20G-109 2,884,497 5/195-9 Steven et al 200-8'8 2,916,677 12/ 1959 Hess 3117-187 2,920,161 1/1960 Dessert et al. 200--9'5 2,925,482 2/ 1191610 Bonanno 200--95 2,939,929 6/11960 Hobson 20G-88 2,945,922 7/ 1960 Bryan 20G- 166 BERNARD A. GILHEANY, Primary Examiner.

R. N. ENVALL, JR., Assistant Examiner. 

7. A CIRCUIT BREAKER HAVING RELATIVELY MOVABLE CONTACTS AND A TRIP DEVICE FOR EFFECTING AUTOMATIC OPENING OF SAID CONTACTS, SAID TRIP DEVICE COMPRISING AN ENERGIZING WINDING, A U-SHAPED CORE MEMBER DISPOSED TO THE ENERGIZED BY SAID WINDING, SAID CORE MEMBER COMPRISING TWO OUTERMOST LAINIATIONS AND AT LEAST ONE INNER LAMINATION, A V-SHAPED PIVOT FORMED ON ONE LEG OF SAID INNER LAMINATION, SAID OUTERMOST LAMINATIONS FORMING SIDEWAY ADJACENT THE OPENING DEFINED BY THE LEGS OF SAID V-SHAPED PIVOT, A MOVABLE ARMATURE COMPRISING TWO OUTERMOST LAMINATIONS AND AT LEAST ONE INNER LAMINATION, SAID INNER LAMINATION COMPRISING A KNIFE-EDGE PIVOTING PORTION PIVOTALLY SUPPORTED ON SAID V-SHAPED PIVOT ON SAID ONE LEG OF SAID CORE MEMBER, SAID ARMATURE EXTENDING OVER THE OTHER LEG OF SAID CORE MEMBER AND BEING SPACED FROM SAID OTHER LEG WHEREBY THERE IS AN AIR GAP BETWEEN SAID ARMATURE AND SAID OTHER LEG, SAID ARMATURE UPON THE OCCURRENCE OF AN OVERLOAD CURRENT ABOVE A PREDETERMINED VALVE THROUGH SAID ENERGIZING WINDING PIVOTING TOWARD SAID OTHER LEG TO CLOSE SAID AIR GAP TO EFFECT AUTOMATIC OPENING OF SAID CONTACTS, SAID SIDE WALLS OF SAID CORE MEMBER ENGAGING SAID PIVOTING PORTION OF SAID ARMATURE TO PREVENT MOVEMENT OF SAID ARMATURE IN A DIRECTION NORMAL TO A PLANE GENERATED BY SAID PIVOTAL MOVEMENT OF SAID ARMATURE, MEANS FOR ADJUSTING SAID TRIP DEVICE BY VARYING THE DIMENSION OF SAID AIR GAP, SAID ADJUSTING MEANS COMPRISING A CAM MEMBER AND A CAM FOLLOWER, SAID CAM FOLLOWER BEING DISPOSED BETWEEN SAID CAM MEMBER AND SAID ARMATURE AND BEING MOVABLE BY MOVEMENT OF SAID CAM MEMBER TO MOVE SAID ARMATURE TO VARY SAID MAGNETIC AIR GAP, AND SAID CAM FOLLOWER BEING ADJUSTABLE TO VARY SAID MAGNETIC AIR GAP TO PERMIT CALIBRATION OF SAID TRIP DEVICE. 